RT Journal Article SR Electronic T1 Screening by deep sequencing reveals mediators of miRNA tailing in C. elegans JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.01.11.426275 DO 10.1101/2021.01.11.426275 A1 Katherine Prothro A1 Karl-Frédéric Vieux A1 Cameron Palmer A1 Isana Veksler-Lublinsky A1 Katherine McJunkin YR 2021 UL http://biorxiv.org/content/early/2021/01/12/2021.01.11.426275.abstract AB microRNAs are frequently modified by addition of untemplated nucleotides to the 3’ end, but the role of this tailing is often unclear. Here we characterize the prevalence and functional consequences of microRNA tailing in vivo, using the C. elegans model. MicroRNA tailing in C. elegans consists mostly of mono-uridylation of mature microRNA species, with rarer mono-adenylation which is likely added to microRNA precursors. Through a targeted RNAi screen, we discover that the TUT4/TUT7 gene family member CID-1 is required for uridylation, whereas the GLD2 gene family member F31C3.2 and, to a lesser extent, PAP-1 are required for adenylation. Thus, the TUT4/TUT7 and GLD2 gene families have broadly conserved roles in miRNA modification. We specifically examine the role of tailing in microRNA turnover. We determine half-lives of microRNAs after acute inactivation of microRNA biogenesis, revealing that half-lives are generally long (median=20.7h), as observed in other systems. Although we observe that tails are more prevalent on older microRNAs, disrupting tailing does not alter microRNA abundance or decay. Thus, tailing is not a global regulator of decay in C. elegans. Nonetheless, by identifying the responsible enzymes, this study lays the groundwork to explore whether tailing plays more specialized context- or miRNA-specific regulatory roles.Competing Interest StatementThe authors have declared no competing interest.